Enhancement of 3-hydroxyvalerate fraction in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) produced by Haloferax mediterranei fed with food waste pretreated via arrested anaerobic digestion integrated with microbial electrolysis cells

Abstract

Bioplastics made of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with a 20 mol% HV fraction are highly desirable in the market for 3-Hydroxyvalerate (HV)-conferred superior thermal, biological, and mechanical properties. Although Haloferax mediterranei (HM) is capable of producing PHBV from food waste, its HV fraction is generally lower than 10 mol%. This study for the first time investigated the engineering approach to increasing HV fraction through elevating the propionic and valeric acid fractions in volatile fatty acids (VFAs) produced from food waste via arrested anaerobic digestion with and without microbial electrolysis cells (MECs) incorporation. Results showed that HV fraction in PHBV produced by HM is proportional to the fractions of propionic and valeric acids in VFAs. A 20 mol% HV fraction can be achieved by MECs incorporation, which might be attributable to pH regulation by the MECs. These findings lay a foundation for developing waste-processing technologies that enable the production of high-value, microbially-derived materials.

Keywords: Bioplastic; Fermentation; MEC; PHA; PHBV; Volatile fatty acid.